Rh(III)-Catalyzed C–C Coupling of Diverse Arenes and 4-Acyl-1-sulfonyltriazoles via C–H Activation

Abstract

4-Acyl-1-sulfonyltriazoles act as versatile carbene reagents in Cp*Rh(III)-catalyzed ortho-selective coupling with arenes via C-H activation. The coupling led to olefination with possible cyclization, depending on the nature of the arene.

Chemoselectivity Switching in the Rhodium‐Catalyzed Reactions of 4‐Substituted‐1‐sulfonyl‐1,2,3‐triazoles with Allenols: Noticeable Differences between 4‐Acyl‐ and 4‐Aryl‐Triazoles

“…Indeed, relaxed scans from INT-4 at different C carbene ···OH confirms the barrierless nature of this insertion reaction (see Figure 3). As depicted in Figure 2, this saddle-point is associated with the simultaneous CÀO bond rupture and formation of the new CÀC bond leading to the observed Z-dioxo-amine in a Claisen type [3,3]sigmatropic rearrangement. [12] As a result of the abstraction of a proton from the OH-moeity by the imine, (Z)-allenyl vinyl ether INT-6 is stereoselectively formed.…”

“…Finally, INT-6 can be directly converted into the observed dioxo-hept-1-enyl-4amine 3 a through the transition state TS in a highly exergonic transformation (~G R = À40.6 kcal/mol) and with a relatively low activation barrier of 15.2 kcal/ mol. As depicted in Figure 2, this saddle-point is associated with the simultaneous CÀO bond rupture and formation of the new CÀC bond leading to the observed Z-dioxo-amine in a Claisen type [3,3]sigmatropic rearrangement. Therefore, our calculations are fully consistent with our initial proposal described above (Scheme 3) based on the proposal by Miura and Murakami.…”

“…[1] This strategy has been built through the use of 4-aryl-1-sulfonyl-1,2,3-triazoles as the source of a-imino metal-carbenes, which may be viewed as donor/acceptor carbenoids. [3] On the other hand, dramatic growth in the synthetic utility of allenes has been noticed in the last decade. [2] Markedly contrasting results were obtained in comparison with donor/acceptor carbenoids.…”

“…[12] As a result of the abstraction of a proton from the OH-moeity by the imine, (Z)-allenyl vinyl ether INT-6 is stereoselectively formed. This species is transformed, by reaction with the allenol, into an (Z)-allenyl vinyl ether intermediate which directly evolves into the observed reaction product through a Claisen type [3,3]-sigmatropic rearrangement. As depicted in Figure 2, this saddle-point is associated with the simultaneous CÀO bond rupture and formation of the new CÀC bond leading to the observed Z-dioxo-amine in a Claisen type [3,3]sigmatropic rearrangement.…”

“…[2] Markedly contrasting results were obtained in comparison with donor/acceptor carbenoids. [3] On the other hand, dramatic growth in the synthetic utility of allenes has been noticed in the last decade. [4] Recently, Miura and Murakami have described the metal-catalyzed reac-tion of 4-aryl-1-tosyl-1,2,3-triazoles with simple allenes to form pyrroles or a,b,g,d-unsaturated imines (Scheme 1b), [5] while we reported the transannulation reaction of 4-aryl-1-tosyl-1,2,3-triazoles with allenols to give 2-pyrrolines (Scheme 1c).…”